In the manufacture of industrial gases from raw gas mixtures the acidic components, and in particular CO.sub.2 and H.sub.2 S, must be separated therefrom. The methanol scrubbing method has proved to be particularly advantageous in that the acidic components are removed at temperatures down to about -70.degree. C. and at pressures to about 80 bar utilizing methanol.
The raw gaseous mixtures which are to be cleaned also generally contain traces of ammonia which tend to concentrate therein due to their high solubility in methanol. Such ammonia concentrations can be desirable, for example as is shown in DE-OS 27 59 123. In patents such as this methods are shown which employ physical scrubbing substances, such as methanol, to which are added small amounts of ammonia, i.e., about 0.05 to 0.5 weight percent. Scrubbing with such additions of ammonia therein thus represents a combined physical-chemical scrubbing so that a relatively smaller amount of scrubbing substance therefore needs to be used.
Such methods, however, are only utilized intelligently when they employ constant ammonia concentrations. However, often the ammonia concentration in the methanol becomes too great so that when carbon dioxide is also present solid precipitates of ammonia carbaminate are formed, particularly in the methanol cold trap for the hydrogen sulphide fraction, and/or the equipment used for heating is influenced and the operation of the scrubbing process can then be disturbed.
It is therefore an object of the present invention to present a method which insures a trouble free and safe flow of the scrubbing methanol used for the removal of these acidic gases from the gaseous mixtures by means thereof.